1. Field of the Invention
The present invention relates generally to semiconductor processing equipment. More particularly, the present invention relates to a susceptor for a pancake reactor and to a method for using the same.
2. Description of the Related Art
As is well known to those of skill in the art, substrate processing typically involved the formation of one or more layers on the substrate. Generally, the substrate, e.g., silicon wafer, was placed on a susceptor in a semiconductor processing reactor. Process gas was introduced into the semiconductor processing reactor, and a layer was formed on the substrate from the process gas.
To insure uniformity in the characteristics of the substrate, it was important that the formed layer was uniform, e.g., in thickness, across the substrate. To enhance the uniformity of the formed layer, the susceptor upon which the substrate was placed was typically rotated within the semiconductor processing reactor.
Rotating susceptors are well known to those of skill in the art. For example, a rotate susceptor is described in Kaneno et al., U.S. Pat. 5,782,979, hereinafter Kaneno. As shown in FIGS. 14A and 14B of Kaneno, wafer trays, which supported the substrates, were formed with wings. As the susceptor rotated, the process gas hit the wings of the wafer trays and caused the wafer trays to rotate within the susceptor. By rotating the wafer trays, the thickness uniformity of the layer formed on the substrates was improved.
It was important to avoid generating or disturbing particulates within the semiconductor processing reactor as these particulates could contaminate and ruin the substrates. Disadvantageously, as process gas flowed through the semiconductor processing reactor, the process gas had a tendency to disturb or dislodge particulates. For this reason, the flow characteristics of the process gas through the semiconductor processing reactor was important and, more particular, it was desirable to have a uniform flow of process gas through the semiconductor processing reactor.
As described above, Kaneno taught that process gas was used to rotate the wafer trays within the susceptor. This improved the uniformity of the formed layer on the substrates. However, at the same time, this disrupted the flow of process gas through the reactor, which increased the tendency of the process gas to dislodge or disrupt particles and contaminate the substrates. Thus, although thickness uniformity was improved, particulate contamination of the substrates was undesirably increased.
In accordance with the present invention, a semiconductor processing reactor includes a rotating susceptor having at least one substrate holder. The semiconductor processing reactor further includes a susceptor motor coupled to the rotating susceptor and a substrate holder motor coupled to the substrate holder. The susceptor motor controls the rotation of the rotating susceptor and the substrate holder motor controls the rotation of the substrate holder.
Advantageously, the rotating susceptor is rotated independent of the rotation of the substrate holder. This allows the rotating susceptor and substrate holder to be rotated in a manner optimum for the particular process being performed within the semiconductor processing reactor. For example, the rotating susceptor and the substrate holder are rotated to optimize the thickness uniformity of layer(s) formed on a substrate supported by the substrate holder.
In one embodiment, the substrate holder includes a pocket and a lift. The lift includes a plurality of tabs corresponding to notches in the pocket. The lift is extended during loading and unloading of the substrate to lift the substrate out of a recess of the pocket and to allow automatic loading and unloading of the substrate.
Advantageously, use of the substrate holder for loading and unloading the substrate is substantially faster and more dependable then manually loading and unloading the substrate. Accordingly, throughput of substrates through the semiconductor processing reactor is maximized which, in turn, minimizes the cost of processing substrates.
In one particular embodiment, the semiconductor processing reactor includes a main driver gear and a driveshaft slidably mounted to the main driving gear. A coupling gear is coupled to the main driving gear and is also coupled to a pocket rotation gear of the substrate holder. Thus, by rotating the driveshaft, the substrate holder is rotated.
The substrate holder further includes a lift and a cross pin. The lift rests on the cross pin. The cross pin includes a pin extending through an aperture of the pocket rotation gear. The pin rests on a lift plate mounted to the driveshaft. By moving the driveshaft up and down, the cross pin and lift resting on the cross pin are likewise moved up and down.
Also in accordance with the present invention, a method includes rotating a rotating susceptor with a first motor and rotating a substrate holder of the rotating susceptor with a second motor. Advantageously, the rotating susceptor is rotated independent of the substrate holder.
In one particular embodiment, a main driver gear is coupled to a coupling gear. The coupling gear is coupled to a pocket rotation gear of the substrate holder. The main driver gear is rotated to rotate the substrate holder.
Also in accordance with the present invention, a method of operating a semiconductor processing reactor includes loading a substrate into a recess of a substrate holder of a rotating susceptor of the semiconductor process reactor automatically and without manual intervention. The rotating susceptor is rotated and the substrate holder is rotated.
To load the substrate, a lift of the substrate holder is extended. The substrate is placed on the lift. The lift is retracted to move the substrate into the recess.
The substrate is processed. The processed substrate is unloaded out of the semiconductor processing reactor automatically and without manual intervention. To unload the processed substrate, the lift of the substrate holder is extended. The processed substrate is removed from the lift. After the processed substrate is removed, in one embodiment, a new substrate, to be processed, is loaded into the recess of the substrate holder automatically and without manual intervention in a manner similar to that described above.